For improving yield of core materials (e.g., strip materials) used for producing laminated cores, there has been known so-called wound cores produced by punching out from a core material not a plurality of continuous segment core sheets in a ring shape but a plurality of segment core sheets in a band shape and winding and laminating the segment core sheets.
In particular, arc-shaped segment core sheets connected together by connecting portions and having a predetermined number of slots are punched out from a core material using dies. Then, the continuous segment core sheets are wound in a spiral form and laminated while the connecting portions located in outer peripheral portions of the segment core sheets are bent and side edges of the adjacent core sheets are fitted with each other. When viewed in a laminating direction of the laminated core, the adjacent connecting portions are in circumferentially different positions and the segment core sheets and the connecting portions are vertically next to each other (See Japanese Unexamined Patent Publication No. 1-264548, Japanese Unexamined Patent Publication No. 8-196061, and Published Japanese Translation of PCT International Application No. 2004-505595, for example).
However, in the conventional art disclosed in the publications, when the connecting portions are bent to position the plurality of segment core sheets in an annular form, bulges are formed in the connecting portions in a thickness direction thereof. The bulges create gaps between the laminated segment core sheets, thereby causing variations in thicknesses of manufactured laminated cores. In the assembly of motors having the laminated cores, for example, extra pressure treatments have been required to eliminate the gaps. Furthermore, the gaps cause reduced efficiency and vibration in the motors, thereby adversely affecting the quality of the motors.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a highly-efficient and high-quality laminated core that is free from effects of bulges formed in the thickness direction of the connecting portions, and a method for manufacturing the laminated core.